Fixes #145 -- fixes loading pkcs7  data from ASN1
Added a test for loading ASN1 data
Py3k fix
Added a docstring
This needs the latest cryptography
Added a changelog entry
Merge pull request #148 from alex/pkcs7-stuff

Fixes #145 -- fixes loading pkcs7  data from ASN1
Merge pull request #1 from pyca/master

Update from origin